The bison in San Francisco's Golden Gate Park, brought to the park by John McLaren in 1891, when the species was teetering on extinction. The current herd, down to six females photographed on Wednesday, October 29, 2008.

Photo: Eric Luse, The Chronicle

The bison in San Francisco's Golden Gate Park, brought to the park...

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A man watches a herd of bison in Golden Gate Park in San Francisco, Calif. on Dec. 3, 1942.

Photo: File, The Chronicle

A man watches a herd of bison in Golden Gate Park in San Francisco,...

The bison in Golden Gate Park are one of San Francisco's most beloved, long-standing and bizarre attractions. They're also getting old, and the city will soon have to decide if it's worth the cost of buying more - and whether they should once again breed the large beasts.

The current herd is made up of six females who are all pretty aged, at least for bison: The youngest is 16, while two others are 17 and three are an ancient 25 years old. Bison, commonly called buffalo, generally only live to 20 or 25, although they have been known to live up to 40 years in captivity, according to experts.

The city still has a few years to decide what to do. The current herd is healthy and recently received $1.2 million for improvements to their digs on John F. Kennedy Drive. Those changes included upgrades to their habitat and a new barn that makes it easier to provide veterinary care to the enormous creatures, which are owned by the Recreation and Park Department and cared for by a zookeeper from the San Francisco Zoo.

"The Recreation and Parks Department will have to make a couple of decisions," said Bob Jenkins, the zoo's vice president for external affairs. "No. 1, do they want to grow the herd? Do they want to have a display herd or a breeding herd? Right now, we have a display herd of all females, and they are getting older and reaching the end of their life expectancy. In a few years, they will be gone."

The bison were originally brought to the park in 1891 by John McLaren, one of the park's founders and first superintendent, when the species was teetering on extinction. The inaugural pair was named after the president, Benjamin Harrison, and actress Sarah Bernhardt.

San Francisco was the first city in the western United States to begin a captive breeding program to prevent the disappearance of bison, which are native to North America and hold a special place in American Indian cultures.

The last time the herd was in danger of dying out, in the early 1980s, then-Mayor Dianne Feinstein's husband, Richard Blum, donated a new group.

For many years before and after Blum's donation, breeding wasn't an issue, because there was at least one male in the herd. According to the zoo, more than 500 calves have been born in Golden Gate Park over more than a century. Many of them lived out their years at the park, while some were taken to other zoos and sanctuaries.

But 18 years ago, after six calves were born in a one year period, officials decided to give the dominant male an epididymectomy (that's bison speak for a vasectomy). That male died in 1997 of liver failure. The current herd - all of whom were acquired from a San Jose meat company, Durham Meats - has been living a bachelorette life for many years.

It's more work to have a bull in the herd, Jenkins said. And while bison cost only around $1,000 apiece, they first have to be quarantined for several months, making the process more costly. The Recreation and Park Department, like all city agencies, is facing hard financial times, and even in a better economy has trouble funding its more than 200 properties.

But city officials said they would be hard-pressed to discontinue the oh-so-San Francisco tradition.

"There's certainly strong support, I belive, for keeping a bison herd in San Francisco," said Recreation and Park Commissioner Jim Lazarus, who expressed interest in bringing in a bull and "letting nature take its course."

"The bison herd is historic," he said.

They also have their own boosters - the Watchbison Committee, which was founded 18 years ago and organizes monthly cleanups of the buffalo's pasture, said longtime member Shelley Fernandez.

Fernandez said her group has been instrumental in pushing a number of changes at the paddock, including the installation of "rubbing stumps" several years back (bison like to scratch their backs on tree stumps) and, in 1993, renaming the herd with American Indian monikers. Before the bison were rechristened, they had Shakespearean names.

"They have a sacred meaning to Indians - they are very connected to the spirit of the buffalo," she said. "Why shouldn't we have buffalo? We have the space there."

The bison are world famous and very popular, agreed Rose Dennis, a park department spokeswoman.

"We receive inquiries from all over the place about the bison because people love them," she said. "It's a unique aspect of the park, and they are uniquely beautiful."

According to Dennis, bison fans should not fret about the herd - "they lead a great life," she said.

She also noted that the department is in a state of influx, as its general manager stepped down several weeks ago and a search is under way for a new, permanent replacement. In the meantime, interim general manger Jared Blumenfeld is being "brought up to speed on a number of issues," Dennis said.